A lot of flamers are actually not that mean irl.
Until recently I thought that all flamers must also be the worst kind of assholes irl too but after seeing some of my friends and colleagues play I found out that this isn't true.
I know these guys, they never were angry or appeared like assholes to me and are actually close friends of mine. Imagine my surprise when I saw them raging super-hard when they played League. They were incredibly toxic, some just in-chat and all you did hear from them in the skype call was heavy breathing and sighing, but some were also raging verbally in voice call . . . pretty annoying.
So for that I basically created this smurf. I told them that I quit league and now I play on this account. I did this because they always invited me into their games which wasn't a nice experience. Now I can finally play in a calm fashion again while not hurting my relationship with them. As an added bonus, I learned something very valuable - flamers aren't necessarily assholes, they just tend to release all the stress and rage that they soaked up irl while playing League and you can't expect them to be reasonable. Of course that is not a great way to deal with their stress and anger but I think that it's still better than them venting it irl.
Just remember this when finding yourself with one of those guys in your games again. Don't even bother arguing back, you can't expect someone to be reasonable who is letting all his or her collected anger out. In actuality, perhaps being nice to them might just help them enough with their anger issues to decrease their toxicity in further games.
Most flamers aren't narcissistic and arrogant assholes, just average humans with some stress and anger management issues. An insight that I had way too late into my League career.